Ch. 11 & 3  IMF & stoichiometry                   test     [95 points]                   AP Chem

For problems involving calculations, show your work in an organized manner, include any relevant equation (or formula and conversion factor(s)), put the proper units in your calculations / answer, and have the proper number of significant figures in your answer. 

Academic Honesty:   The answers on this test are my own and I am using only the allowed set of notes as described in the syllabus.  I have not discussed the test questions with anyone before or during the test nor have I seen the test questions prior to the exam.  If you violate any of the preceding items or do not sign, your semester grade is a F.

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1.  What is the % yield in the reaction:  5.0 g C₂H₆  +  15.0 g O₂  à  CO₂  +  5.0 g H₂O ?  [20 points]

2.  1.00 g C_xH_yO_z   +  excess  O₂  à   2.00 g CO₂  +  0.818 g  H₂O.    [20 points]

a.  What is the empirical formula of the compound ?

b.  The molar mass of the compound is 88 g / mole; what is its chemical formula ?

3.   What is the relative vapor pressure of HCl versus HBr ?  Justify your response.  [hint:  this is a “trick” question; 10 points]

4.  Which compound, carbon tetrachloride versus carbon tetrabromide, would have the larger boiling point ?  Justify your response; use and define the term, polarizability, in your response.  [15 points]

5.  Describe the graphical analysis to determine the enthalpy of vaporization, ΔH_vap, using the Clausisus-Clapeyron equation

state the experimental data needed in such an analysis.  [10 points]

6.  Sketch the vapor pressure versus temperature graph for dimethyl ether (i.e. ether with 2 methyl groups) versus ethyl alcohol (i.e. alcohol with an ethyl group); put both curves on the same graph; identify the curve for the ether versus alcohol.  Justify your response.  [20 points]